Sunday, March 8, 2015

Every couple of months I'll get a call from a person who
heard that a friend or a coworker has meningitis and wants to know what to do
about it. Meningitis can be deadly. Some of the bacteria that can cause
meningitis are transmitted from person-to-person. People who have had contact
with a person with certain types of meningitis should be treated with
antibiotics to prevent illness.

Nevertheless, my immediate response is usually a variation
of the cover of The Hitchhiker's Guide to the Galaxy:
Don't panic. My first clue that it's
not something that the caller should worry about is the fact that I'm hearing
it from a friend or coworker first and not from a doctor or a microbiology
laboratory. The pathogens require a public health response are notifiable conditions, which means that health care providers and laboratories are
required to notify the local health department of the county in which the
patient lives.

Meningitis means inflammation of the meninges. The meninges
are the membranes that cover the brain and spinal cord. There are three layers,
the pia mater ("gentle mother"), arachnoid mater ("spider mother,"
because of its cobweb-like appearance), and the dura mater ("tough
mother"). Meningitis is characterized by fever, headache, altered mental
status, and stiff neck. Seizures and photophobia
(discomfort in response to light. Imagine walking out of a dark room into bright sunlight) may also occur.

There are a lot of things that can cause meningitis:
bacteria, viruses, funguses, parasites, drugs, chemicals, tumors, or anything
that can cause meningeal inflammation. The central nervous system (CSN) is a sterile site, so most microorganisms that
pass though the blood-brain barrier can cause meningitis (more about that later). Relatively few of the
infectious causes of meningitis are transmissible from person-to-person. Many
of the bacteria that can cause meningitis are normal flora; that is,
they are normally present on or in our bodies. The viruses that most commonly
cause meningitis usually do not cause severe illness in most people. Fungal and
parasitic meningitis are rare.

There are three vaccine-preventable causes of bacterial
meningitis: Haemophilus influenzae type B (Hib),
Neisseria meningitidis (meningococcus), and Streptococcus pneumoniae (pneumococcus). I plan to go into more
detail about each one of those in future entries. There are several risk
factors for the different types of bacterial meningitis. Streptococcus agalactiae (Group B
streptococcus) is the most common cause of bacterial meningitis in newborn
babies. Listeria monocytogenes also affects
newborn babies as well as adults over 60 years of age and people who are immunosuppressed.
Neurosurgery and head trauma can increase the risk of meningitis from bacteria
normally found on the skin. Gram negative bacteria, including bacteria that are normally found in the gut, can also
cause bacterial meningitis. In the March 2015 issue of the American Journal of
Tropical Medicine and Hygiene there is a case series of people
who developed bacterial meningitis as the result of strongyloidiasis,
an infection with a parasitic worm that can migrate throughout the body.

Bacterial meningitis can be fatal or cause serious long-term
problems. It is treated with antibiotics, however, because many antibiotics do
not easily cross the blood-brain barrier, treatment can require high doses of
antibiotics, treatment with several antibiotics, toxic antibiotics, prolonged
treatment, or antibiotics that easily cross the blood-brain barrier but are not
as effective as those than do not. In some severe cases of bacterial
meningitis, antibiotics have been injected directly into CSF. Also, some of the bacteria that cause
meningitis are resistant to antibiotics, making treatment much more difficult.

Lumbar puncture ("spinal tap") is one of the most
important diagnostic tests for meningitis. A needle is inserted into the spine
below the spinal cord to collect cerebrospinal fluid (CSF). CSF is normally clear and colorless. Cloudy CSF is caused by a high number of white blood cells
present in the fluid and is indicative of bacterial meningitis. In addition to microscopic analysis of CSF, the amounts of glucose and protein are usually measured and the fluid can be cultured
to identify bacteria present in the fluid. Aseptic meningitis is the term used
when bacteria do not grow from a CSF culture. It has become synonymous with viral
meningitis, but tuberculous meningitis and syphilitic meningitis can also be aseptic.

Parasites that can cause meningitis include amebas and
worms. Naegleria fowleri is a free-living
ameba that causes primary amebic meningoencephalitis (PAM). The infection,
which is almost always fatal, is acquired by swimming in warm water or through sinus rinsing.
Naegleria has been found in public water systems in Louisiana and there have been two deaths from PAM that
were associated with sinus rinsing.

Rat lungworm (Angiostrongylus cantonensis) causes eosinophilic meningitis in
humans. As the name suggests, rats are the definitive host of A. cantonensis. Snails
and slugs are intermediate hosts. Humans (accidental or dead-end hosts)
are infected by eating snails or eating vegetables contaminated with snail or
slug slime. A. cantonensis is not
native to the continental U.S., but it has been found in Louisiana and
was recently found in Florida.
Although the worms migrate through the brain, the disease is self-limiting, requires no specific treatment, and
usually does not cause long-term complications. Baylisascaris procyonis (raccoon
roundworm), Gnathostoma species, Taenia solium (pork tapeworm), and Toxocaraspecies (cat
and dog roundworms) can also cause eosinophilic meningitis. These worms cannot
reproduce in the central nervous system and eventually die. Treating these
infections with anthelmintic
drugs can sometimes cause more inflammation than allowing the worms to die on
their own, so the goal of treatment is to reduce inflammation and treat any
complications of the infection.

As I mentioned above, I plan to write more about Hib,
meningococcus, and pneumococcus, but there are some other topics I would like
to address first, including some that were raised by people who responded to my HB 2009 entry.

Sunday, February 22, 2015

Over the last several weeks I've read comments in op-ed
pieces and on social media about the measles epidemic that began at Disneyland.
There is one comment that I have read several times that troubles me:

"No one has died."

That may be true, but 20% of people with measles have been
hospitalized with measles or complications of measles so far during this
outbreak. During the first five months of 2011, 40% of people with measles were
hospitalized. Measles is not a benign disease. Complications
include pneumonia,
encephalitis,
otitis media (middle ear infection), seizures, and diarrhea.

There were a dozen measles deaths reported in the U.S. between 1999
and 2013. Five of those deaths were measles complicated with encephalitis, 3
were measles complicated with pneumonia, and 4 were reported as measles without
complications. The last column is deaths from subacute sclerosing
panencephalitis (SSPE).

Measles deaths, United States, 1999-2013

Year

Encephalitis

Pneumonia

Uncomplicated measles

Measles total

SSPE

1999

1

1

2

5

2000

1

1

5

2001

1

1

2

2002

5

2003

1

1

2004

1

2005

1

1

2

2006

3

2007

3

2008

3

2009

1

1

2

2

2010

2

2

2011

4

2012

2

2

1

2013

1

Total

5

3

4

12

37

Subacute sclerosing panencephalitis (SSPE) is a rare and almost always fatal complication of
measles. It is caused by persistent measles virus infection in the brain. The
virus fails to complete replication and release from infected neurons and glial cells. The onset of
SSPE usually occurs around 7 years after the person had measles, but can occur as soon as 2 years later or as long as 15 years later. The
symptoms begin with personality changes, behavioral changes, and poor scholastic
performance. The symptoms can be subtle and only recognized when more severe
symptoms begin. The disease progresses with muscle jerking and twitching (myoclonus),
seizures, and other movement and muscular disorders; difficulty controlling
movements, difficulty walking, uncontrollable movements, and spasticity.
The final stage SSPE is characterized by weakness in all four limbs, inability
to speak, blindness, uncontrolled sweating, and uncontrolled changes in blood pressure,
heart rate, and temperature. Death usually occurs 1 to 3 years after the onset of
symptoms. The risk of SSPE is highest in people who had measles as infants. Wild-type measles viruses cause SSPE. There is no evidence
that measles vaccine virus causes SSPE.

A couple of deaths every year or so might not seem like a
lot, but let's set the record straight: people in the U.S.
are hospitalized with measles and people in the U.S. die from measles.

Centers for Disease Control and Prevention, National Center
for Health Statistics. (2015). Multiple Cause of Death 1999-2013 on CDC WONDER
Online Database. Accessed February 22, 2015 at http://wonder.cdc.gov/mcd-icd10.html.

About Me

Registered Nurse, 1992 to present;
Certified Neuroscience Registered Nurse, 1995-2015;
Diploma in Clinical Tropical Medicine and Traveler's Health, 2000;
Married Holly in 2005;
Bachelor of Science in Nursing, 2006;
Master of Public Health and Tropical Medicine, 2009; Father, 2012; Member of the American Society of Tropical Medicine and Hygiene